Why inequality undermines societies – an evolutionary perspective

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This article originally appeared on Contributoria, at .

The level of economic inequality within countries has been linked to a range of worse health and social outcomes. Evidence from the evolutionary behavioural sciences of how we have evolved to react to our environment may shed light on why we fail to flourish under extreme inequality.

Five years ago The Spirit Level was published, bringing into the mainstream the evidence on the harms of economic inequality. The two academics behind the book, Richard Wilkinson and Kate Pickett, drew on research in the various social science disciplines involved in their day jobs. They went beyond their own field of social epidemiology to show that more unequal societies are not only less healthy, but have worse outcomes on myriad other measures. It’s worth listing these to emphasise the diversity of inequality’s ill effects: infant mortality, child wellbeing, educational attainment, teenage births, social mobility, obesity, mental health, drug abuse, trust, altruism and cooperation, violence and homicide, imprisonment, foreign aid, and environmental sustainability. In the years since the book was published, inequality has become a major political issue internationally.

The explanations which are put forward to explain the effects of inequality usually focus on our immediate responses. Biologically, our levels of stress hormones rise; behaviourally, we become more prone to compete and be aggressive with others; psychologically, we become anxious and obsessed with our social status. But that’s where most explanations stop asking why – short of asking ‘why do we respond in these ways to inequality?’ On one level, it’s sufficient to know the proximate causes and ignore the ultimate causes, but this misses an opportunity to learn something instructive about human nature.

“Why do we respond in these ways to inequality?”

To go beyond the visible and measurable factors, a more expansive timeframe is needed. As a species we evolved over millions of years – for physical traits, this is uncontested scientifically. There is more vigorous debate over the extent to which mental traits have been subject to natural selection. Evolutionary psychology is often thought to portray traits as genetically determined, innate and fixed. While this is an approach that some academics take, it is clearly inappropriate to apply this to the inequality evidence. However, the responses to inequality appear to be consistent across societies. This indicates that there are adaptive traits which respond to inequality systematically – we have evolved the ability to adjust to our current situation.

This principle of calibration to the environment is well established in the evolutionary field of life history (LH) theory. It characterises a strategy which we take throughout life as a trade-off between growth and reproduction. At any given time, we can invest (unconsciously!) biological resources in growth at the expense of reproduction, or vice-versa. Ideally, we would take time to grow for as long as possible to ensure long-term health, before bringing the next generation into the world. This wasn’t always possible in the ancestral environment we evolved in – famine, war, diseases and other components of ‘environmental harshness’ all reduced life expectancy. With such considerations, it would have been no good taking your time to develop, only to die before you could reproduce. Rather, the onus is on as quickly as possible getting to a state where you can pass on your genes.

What results from the trade-off is a scale of LH strategies from slow to fast. In an uncertain environment, early maturation and reproduction protect against the risk of dying before reproducing. Other traits typical of the fast LH strategy include having more children, as a hedge against high infant mortality, and investing less parental care in them, be it shorter breastfeeding duration or father absence. Babies are born smaller, which leads to lower adult height, but with an increased risk of obesity and certain chronic diseases later in life.

The obvious objection to applying LH theory to modern problems is that thanks to developments of civilisation like modern medicine, sanitation, and the rule of law, we no longer really need to worry about making it to adulthood. But we’ve simply not had enough time to evolve and adapt to our new environment. The result is a mismatch between the environment we are adapted to and the one we find ourselves in. This is why we still respond to cues of environmental harshness.

It appears that inequality is a cue of environmental harshness which accelerates LH strategies. This is understandable in the context of access to resources – food, shelter, social capital – which are essential to survival. But egalitarianism was the norm for our early human ancestors. They lived in bands of hunter-gatherers, where meat was shared equally in the group regardless of who killed it. We can infer this from the archaeological record, as well as anthropological reports of the few remaining tribes of hunter-gatherers. In these groups, counter-dominance strategies like ridicule and ostracism prevent any one individual from gaining too much power.

“Egalitarianism was the norm for our early ancestors”

Groups became unequal with the advent of agriculture and other developments. Again, this may be too recent for evolution to have taken effect. However, we may have adapted to inequality in ancestral groups of hierarchical primates, prior to the emergence of the Homo genus. Either way, inequality seems to elicit faster LH strategies, whether as a functional adaptation or not.

Our response to inequality goes beyond behaviour directly related to reproduction. Natural selection will have acted on aspects of our biology, psychology and behaviour to form a coherent suite of responses to the social environment. For instance, the rational reaction to living with social stratification is to compete for all you can get, as you’re not guaranteed a fair share. Appeasing those above you in the pecking order while exploiting those below you is the usual result –the opposite of the healthy disrespect for authority found in the egalitarian groups. Sycophantic worship of celebrities alongside demonization of people at the lower end of society may be the modern-day version of these social processes.

The cluster of traits associated with the fast LH strategy share the theme of short-termism. This even extends into the choices we make, in the form of a cognitive bias known as future discounting. When offered the choice of a smaller reward now or a larger reward at a certain point in the future, some are better than others at resisting the temptation of instant gratification. But when the long-term future is uncertain, it’s rational to discount it and take what you can get today. This is another trade-off, between taking a hit for a bigger payoff in the long run, or short-term benefits at the expense of long-term costs.

“When the future is uncertain, it’s rational to take what you can today”

LH strategy has a strong social gradient – lower socioeconomic status (SES) tends to mean a faster LH strategy. Returning to the health and social outcomes of The Spirit Level, a recurring theme is that most of them show a social gradient, with worse outcomes at lower SES. What Wilkinson and Pickett demonstrated was that outcomes that are associated with deprivation are also associated with inequality in itself: average outcomes are worse in more unequal societies. It may be that LH traits follow the same pattern, and that the well-established link with SES can be extended to inequality.

Indeed, the effects of inequality seem to reflect the consequences of the fast LH strategy. More babies being born underweight leads to higher infant mortality. Less parental investment in children lowers child wellbeing. An obsession with social status exacerbates depression and anxiety. A bias to discount the future shortens perceived time horizons, leading to lower educational attainment and lower impulse control in drug abuse. Sustainability and climate change are similarly neglected by a short-term perspective. And a general quickening of life stages shortens childhood, increases teenage births and curtails healthy lives.

Excess inequality can be added to deprivation as a scourge that stunts our growth and flourishing. This inevitably follows from our evolved tendency to react to our social environment. What this means for social policy is that outcomes which have been seen as pathological must be reappraised as contingent responses to our circumstances.

This doesn’t mean that they should be accepted of course. But interventions like education campaigns that appeal to reason can’t solve social problems, when social conditions affect our biology, psychology and behaviour through mechanisms which are outside of conscious control. To get to the root cause, society must be made more equal.

References

Inequality

Flannery, K. (2012). The creation of inequality: how our prehistoric ancestors set the stage for monarchy, slavery, and empire. Harvard University Press.

Wilkinson, R. G., & Pickett, K. (2011). The spirit level. Penguin, London

Life History Theory

Brumbach, B. H., Figueredo, A. J., & Ellis, B. J. (2009). Effects of Harsh and Unpredictable Environments in Adolescence on Development of Life History Strategies: A Longitudinal Test of an Evolutionary Model. Human Nature (Hawthorne, N.Y.), 20(1), 25–51. doi:10.1007/s12110-009-9059-3

Dickins, T. E., Johns, S. E., & Chipman, A. (2012). TEENAGE PREGNANCY IN THE UNITED KINGDOM : A BEHAVIORAL ECOLOGICAL PERSPECTIVE, 6(3), 344–359.

Ellis, B. J., Figueredo, A. J., Brumbach, B. H., & Schlomer, G. L. (2009). Fundamental Dimensions of Environmental Risk. Human Nature (Vol. 20, pp. 204–268). doi:10.1007/s12110-009-9063-7

Figueredo, a, Vasquez, G., Brumbach, B., Schneider, S., Sefcek, J., Tal, I., … Jacobs, W. (2006). Consilience and Life History Theory: From genes to brain to reproductive strategy. Developmental Review, 26(2), 243–275. doi:10.1016/j.dr.2006.02.002

Griskevicius, V., Ackerman, J. M., Cantú, S. M., Delton, A. W., Robertson, T. E., Simpson, J. a, … Tybur, J. M. (2013). When the economy falters, do people spend or save? Responses to resource scarcity depend on childhood environments. Psychological Science, 24(2), 197–205. doi:10.1177/0956797612451471

Kruger, D. J., Munsell, M. A., & French-turner, T. (2011). USING A LIFE HISTORY FRAMEWORK TO UNDERSTAND THE RELATIONSHIP BETWEEN NEIGHBORHOOD STRUCTURAL DETERIORATION AND ADVERSE BIRTH OUTCOMES, 5(4), 260–274. Nettle, D. (2010). Dying young and living fast: variation in life history across English neighborhoods. Behavioral Ecology, 21(2), 387–395. doi:10.1093/beheco/arp202

Future discounting

Daly, M., & Wilson, M. (2005). Carpe diem: Adaptation and devaluing the future. The Quarterly Review of Biology, 80(1), 55-60.

Griskevicius, V., Ackerman, J. M., Cantú, S. M., Delton, A. W., Robertson, T. E., Simpson, J. a, … Tybur, J. M. (2013). When the economy falters, do people spend or save? Responses to resource scarcity depend on childhood environments. Psychological Science, 24(2), 197–205. doi:10.1177/0956797612451471

Other

Scott-samuel, A., Bambra, C., Collins, C., Hunter, D. J., Mccartney, G., & Smith, K. (2013). THE IMPACT OF THATCHERISM ON HEALTH AND WELL-BEING IN BRITAIN, 44(1), 53–71.

Whiten, A., & Erdal, D. (2012). The human socio-cognitive niche and its evolutionary origins. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 367(1599), 2119–29. doi:10.1098/rstb.2012.0114

Image Paul Anderson [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)%5D, via Wikimedia Commons

Evolutionary insights for public policy

The significance of an evolutionary approach to public health is increasingly being recognised. The negative effects of poverty and inequality are also being recognised as a huge burden on health. Occasionally, the two are even combined to acknowledge our evolved responses to inequality.

Overall though the various efforts seem to have stopped short of explicitly proposing an evolutionary explanation to the Spirit Level evidence between countries. Understandably, the focus has been on measures like teenage pregnancy and breastfeeding rates that directly measure life history (LH) strategy (see this post on LH theory). But other outcomes may be the result of a faster LH strategy too: infant mortality may be higher in more unequal countries because of a reduced biological investment in each child, leading to low birthweight and prematurity.

The other outcomes in the Spirit Level can be brought under the life history strategy umbrella too, with its general principle of short-termism. The harsher and more unequal the social environment, the more uncertainty there is over long-term prospects. This would have been true in our ancestral environment too, and with morbidity and mortality rates so much higher, the selection pressure on behavioural strategies would have been extremely strong. The danger of dying before or during reproductive years made early reproduction paramount. As a result, we evolved a comprehensive response to harshness, which speeds up the course and development of key life stages, and prioritises reproduction over growth.

The response is evident in various domains:

Biologically, periods of growth are shortened, and puberty is brought forward. As in Barker’s thrifty phenotype hypothesis, where less important organs like the pancreas get less energetic investment when energy is scarce, physical size is sacrificed to allow reproduction to occur earlier. This under-investment early on in life may lead to the various health problems that develop later. Of course middle-aged health problems wouldn’t have been a major problem evolutionarily, if the early reproduction meant that your genes had been passed on in a difficult environment. They may not even have developed, with an environment of low calorie availability and an active lifestyle avoiding the metabolic disorders seen today. The molecular symptom of quicker development is oxidative stress, which is a measure of the biological stress on an individual. It is linked with chronic low-level inflammation and suppression of the immune system. Heightened cortisol levels, and activation of the hypothalamic-pituitary-adrenal axis which releases adrenaline, are also implicated. The response to stress is complex, but the various measures are consistently related to low socioeconomic status, and so can be argued to be part of the fast LH strategy.

Cognitively, people show a higher rate of a cognitive bias known as future discounting. This involves taking smaller, short-term gains at the expense of larger, long-term ones. Delaying gratification and impulse control require a low rate of future discounting.

Behaviourally, this bias could be argued to underlie almost any of the behavioural problems in the Spirit Level – drop-out rates from high school and low educational attainment, unsustainable environmental practices, addiction of any kind, from gambling to alcohol and drugs. Public goods problems (like climate change) require a long-term assessment of costs and benefits, so a bias to discount the future is disastrous for agreements on action. Hierarchy also encourages conspicuous consumption to signal status – another unsustainable practice. Future discounting may explain why trust is lower in more unequal countries, as a long-term view is needed to help someone today, when you may not be paid back for a while.

Parental investment is another feature which is sacrificed in the fast LH strategy. This is seen in harsher parenting styles. Parental inconsistency has been linked with elevated levels of stress hormones in children. And one of the parents may not even be there – 26% of families in 2011 were single-parent households. Absent fathers account for the vast majority of these. The effect on boys is the development of excessively masculine traits; girls hit puberty earlier. Both genders are more likely than average to repeat their parent’s lifestyle. The UNICEF index of child wellbeing correlates negatively with inequality, as do childhood behavioural problems.

Consequently, mental health suffers in unequal societies – especially anxiety. This can’t be said to be adaptive in modern society, but as with chronic stress, it is possible to theorise how it could have helped in an ancestral environment. In small doses, anxiety and low mood may have been one way of avoiding conflict, by avoiding aggression from others. But as with stress, constant exposure is pathological.

Inequality, by stratifying the social hierarchy, favours competition over cooperation as the way we interact with each other. Status becomes more important, as it has always signalled an ability to access resources, including mates. Excessive inequality means that those at the top can monopolise resources, and those at the bottom have nothing to lose when they try to climb the ladder. This manifests itself in higher rates of violence and homicide. Men may go to greater lengths to keep partners as well as compete for them, using violence and sexual coercion. The violence statistics don’t include sexual violence due to international differences in definitions, but (not unrelatedly) the status of women and gender equality are better in more equal countries.

In order to bring about the policy changes necessary to reduce inequality, disparate interest groups need to be made aware of the wide-ranging effects of inequality and the associated LH traits, in order to campaign with a louder voice together. This means physical and mental health organisations, alcohol and drugs charities, violence reduction schemes and so on could benefit from coming together to work for something that would tackle all of their respective issues at source. It’s not about creating a ‘natural’ environment – there’s no such thing, as we adapt to vastly different societies. It’s recognising that a more equal society brings out the best of our nature.

Life History Theory and Inequality

Here’s a longer piece on how inequality is activating an evolved strategy of living fast and dying young. It’s a theory of the evolutionary logic behind the seemingly maladaptive behavioural responses to inequality which cause so many health and social problems. A great article along the same lines can be found here.

 

Abstract

Life history theory has been used to explain clusters of socially problematic behaviour, which are often theorised to be a response to deprivation. In social epidemiology, income inequality has repeatedly been posited as a contributing factor in a wide range of negative health outcomes, independently of average income. Various other social problems have been linked with income inequality at a population level. Both life history strategy and outcomes associated with inequality show a social gradient – strategies are faster and outcomes are worse in lower socioeconomic status groups. The evolutionary rationale of life history strategy is to use behavioural flexibility to respond appropriately to the environment. Harshness and unpredictability engender faster strategies, and inequality may be a signal of these properties. Inequality manifests itself with a positive skew, which disadvantages a disproportionate section of a group. Additionally, status hierarchies which are more stratified in more economically unequal societies are psychologically salient and may act as an independent cue. As such, inequality is predicted to favour faster life history strategies, resulting in the worse outcomes that have been linked with inequality. Faster development, earlier reproduction, future discounting and heightened social competition contribute to problems like teenage pregnancy, worse health behaviours and homicide. The mechanisms by which inequality affects the various traits of life history strategy need to be elucidated in more detail. Reducing inequality would be a way of preventing some of the harms of the fast life history strategy.

 

Life history theory

Attempts have been made to apply evolutionary psychological research to public policy on issues like teenage pregnancy (Dickins, 2012) and substance use (Richardson & Hardy, 2012). This approach draws heavily on life history (LH) theory; which proposes that humans react flexibly to environmental conditions. Facultative behavioural strategies have evolved in response to variation in our ancestral environment, and the strategies develop under the influence of environmental circumstances. LH theory usually refers to either the harshness or unpredictability of environments as influencing the development of fast or slow LH strategies (Ellis et al., 2009).

A LH strategy is a coherent cluster of behaviours which is adaptive to the survival and reproductive constraints of the environment. So a fast LH strategy involves traits like early menarche and pregnancy, a higher number of low birthweight offspring, shorter birth spacing, shorter breastfeeding, lower parental investment, smaller adult body size and lower longevity. This strategy evolved to minimise the risk of death before reproduction, spread the risk of offspring mortality, and prioritise reproduction over growth – adaptations to harsher or more unpredictable environments (Ellis et al., 2009). In industrialised societies, despite early mortality rates being negligible compared to those in the environment of evolutionary adaptedness (EEA), there must still be cues that modulate LH strategies.

Income inequality

Figueredo (2006) linked the cluster of behaviours that constitute the fast LH strategy to co-occurring socially undesirable behaviour in a wide range of bodies of research, from those in drug abuse to divorce to psychopathology. Similarly, though at a population rather than individual level, income inequality is a predictor of numerous problem health and social outcomes, both in rich countries and in the 50 American states (Wilkinson & Pickett, 2009) – unless otherwise stated, this is the source of all correlations with income inequality. A number of these outcomes are also predicted by the fast LH strategy. Outcomes which are worse in more unequal countries have a social gradient – they are more common in lower socioeconomic status (SES) groups. The fast LH strategy shows a similar social gradient. In general though, LH theory tends to be used to explain differences between either species or individuals – differences between groups are either by SES (e.g. Nettle, 2010a) or comparing subsistence to industrialised societies. LH theory is not usually used to explain differences between industrialised countries with similar average SES.

Health and social outcomes

Teenage pregnancy is a direct measure of LH strategy, and rates are higher in more unequal countries. Dickins (2012) proposed a LH approach to understanding teenage pregnancy in the UK, with relative poverty as a driver.

Other measures can be argued to be indirect measures of LH strategy. Infant mortality is higher in more unequal societies, which may be due to lesser maternal physical investment in each child – average birthweight is lower in more unequal countries. The slow LH strategy minimises the risk of infant mortality and ill health (Figueredo, 2006), whereas health is traded off for earlier reproduction in the fast LH strategy. Inequality predicts worse health outcomes later in life too, for instance higher rates of obesity. Metabolic syndrome, which includes central fat deposition and insulin resistance, can be programmed during early life by changes in the nutritional environment (McMillen & Robinson, 2005). This is thought to be a facultative LH response to unpredictable food supply. It is not clear why inequality would trigger this response, though it may be due to dominance status having determined access to resources in the EEA. Stratified incomes may represent a stratified dominance hierarchy, which puts a premium on status, with low status associated with poor access to resources. Adult body size is another LH trait that is predicted by inequality – height correlates negatively with inequality, conversely to obesity. Longevity is sacrificed in the fast LH strategy, and life expectancy too is lower in more unequal countries (Wilkinson & Pickett, 2009).

Daly et al. (2001) demonstrated that the best predictor of homicide rates in American states and Canadian provinces is income inequality. This relationship holds in a between-country analysis of homicide rates and inequality. Income inequality correlates negatively with life expectancy, but Wilson and Daly (1997) found that inequality has an additional effect to that of life expectancy on homicide rates. International data on crime are non-comparable, but imprisonment rates are higher in more unequal countries. Educational attainment also correlates negatively with inequality. This could be due to the lack of long-term investment in the fast LH strategy.

Mental illness is more common in more unequal countries. This could be due to the highly stressful fast LH lifestyle, with lower levels of social support. Richardson & Hardy (2012) employed a LH approach coupled with a dual process cognitive model to explain substance use. Illicit drug use is higher in more unequal countries. Faster, implicit processing was linked with a fast LH strategy, in particular in unpredictable environments where deliberative processing of context and outcomes is less likely to be valid over time. Other outcomes in Wilkinson & Pickett (2009) as diverse as recycling rates, child wellbeing and women’s status could be argued to result from the fast LH strategy.

An important aspect of the inequality evidence is that not just low SES groups benefit – even higher SES groups show better outcomes compared to their counterparts in more equal countries, on measures like mortality rates, literacy rates, and various health measures (Wilkinson & Pickett, 2009). This suggests that inequality has an effect independent of deprivation.

A case can be made for traits in the fast LH strategy contributing to most of the measures that correlate with income inequality. There could be links between impulsivity and imprisonment, low social support and mental illness and so on.

Does income inequality affect life history strategy?

The high incidence of fast LH traits in unequal countries suggests that inequality, or an aspect of the environment linked to inequality, is a salient cue for LH strategy. It is important to note that correlating the average wealth of rich countries as measured by gross national income (GNI) per capita with the health and social outcomes covered above does not produce significant relationships. Humans are highly attuned to dominance status, and it is likely that we process inequality much like a dominance hierarchy.

The two main properties of the environment that calibrate LH strategy are environmental harshness and unpredictability. It is feasible that inequality is used as a signal of unpredictability, with more variance in people’s circumstances being interpreted as higher unpredictability in access to resources. Inequality may be used in this way to complement longitudinal experience of unpredictability, especially by children. Inequality would be salient to everyone regardless of SES, and so could explain why inequality has an effect across the income distribution.

Environmental harshness is the other main driver of the fast LH strategy, and inequality may act as a cue of harshness, or possibly uncontrollability – the inability of avoiding a deleterious event (Brumbach et al., 2009). Social mobility is highly negatively correlated with income inequality (Wilkinson & Pickett, 2009), so the more unequal a society, the less an individual can negate the risks associated with low SES by investing in growth and fewer offspring. The higher extrinsic mortality rate may change the adaptive value of various preventative health behaviours, so explaining their social gradient (Nettle, 2010b). Pickett et al. (1997) posit that homicide rates and teenage pregnancy may be evidence of a sex-differentiated response, with males increasing social competition and females changing their reproductive scheduling. It may be that income inequality is a more salient cue for social competition, whereas life expectancy has more of an effect on reproductive scheduling.

Inequality may signal harshness due to how resources are distributed. By definition, the income distribution becomes more platykurtic (flatter). But additionally, the distribution shows more of a positive skew – there are more people on a comparably low income below the mean, with income and wealth disproportionately concentrated in a small section of the group. Similarly in other hierarchical animals, access to resources like food and mates is often monopolised by a few dominant individuals. While early humans lived in egalitarian bands of hunter-gatherers, both our more primitive and recent evolutionary environments had varying levels of inequality.

It is this skewed distribution, rather than just inequality itself, that is predicted to have been evolutionarily relevant. It appears that inequality reliably manifests itself in this way, favouring the few over the many. The skewed access to resources means that a large proportion of individuals are at a serious disadvantage in the evolutionary essentials of survival and reproduction. In more equal societies by comparison, a much larger proportion of individuals has the means to succeed evolutionarily. The distribution of evolutionary success as measured by survival and reproduction is determined by the distribution of vital resources. The distribution of these resources is mirrored in the income and wealth distribution, because money is the best available measure of access to resources in modern societies.

Faster LH strategies are expected to be triggered by inequality. Evolutionarily, living in unequal groups would have meant a greater risk of lacking resources, increasing the risk of dying before being able to reproduce. Reproductive schedules would have been shortened accordingly. The fact that high-ranking individuals have greatly preferential access to mates means that many males are at risk of not fathering any offspring. As a result, social competition is intensified. In modern societies there is little chance of dying before reaching reproductive age, so the response of early reproduction results from a mismatch between the ancient and modern environment.

Evidence from other literatures

Some evolutionary approaches have offered a functional explanation of other effects of inequality. The average personality is less agreeable in more unequal American states – a response to intensified competition and individualism (de Vries et al., 2011). A preference in women for men with more masculine faces is stronger in countries with lower scores on a health index (DeBruine et al., 2010), which could be adaptive because facial masculinity is thought to signal better health. But a measure of within-country income inequality was found to correlate more strongly with masculinity preference – this could be adaptive because facial masculinity also signals social dominance, which is of more importance in more stratified societies (Brooks et al., 2011).

The difference between male and female mortality rates is predicted by the level of economic inequality in a country – the more unequal a country is, the bigger the sex difference in mortality rates (Kruger, 2010). This finding is consistent with the concept of males showing a bigger increase in competitive behaviour in response to increasing inequality, compared to females, with excess mortality rates driven by external mortality caused by risk-taking behaviour (Wilson & Daly, 1997). Trust is another trait which has been found to vary with inequality. Neville (2012) found that academic plagiarism was more common in US states which had higher levels of economic inequality. This relation was fully mediated by a measure of trust. A functional explanation of inequality reducing trust is proposed, with students evaluating “whether they can afford to behave uprightly when fellow students benefit from dishonesty.”

A different line of evidence on trust comes from public goods games, where players in a group have the choice of contributing from their own resources to the public good, or keeping their own money and free-riding. Wealth inequality between players has a corrosive effect on contributions to the public good, but only when the inequality is made known to the players (Anderson et al., 2004). This mirrors the strong link between income inequality and trust in rich countries. Lack of trust could be understood as a response to elevated levels of social competition, in turn driven by higher payoff variance.

Taken together, the wide range of behavioural effects that have been linked with inequality can be considered a behavioural syndrome that is triggered by excessive inequality. While the various behaviours have already been conceptually grouped (into the fast LH strategy), only individual behaviours have been linked to inequality. The phenomena linked to inequality by social epidemiologists reflect the fast LH traits or their effects, either through faster reproductive scheduling or heightened social competition which lowers cooperation and trust.

Future directions

As the theoretical groundings are interdisciplinary, research could proceed in a number of different fields. Other traits of a fast LH theory that haven’t yet been linked with income inequality could be investigated as they would be predicted to be more widespread in more unequal areas. Candidate traits include the number of offspring per mother, the number of men a woman has children by, and average age at menarche and sexual debut. Such enquiries would be limited by the existence of international data on the traits; more local areas have the advantage of having more potentially confounding factors constant, but income inequality doesn’t always correlate with outcomes over smaller areas (Wilkinson & Pickett, 2009). Additionally, if it is the distribution of income which is the important thing about inequality, median income should be a better predictor of outcomes than mean income or GNI per capita.

The proximate psychological mechanisms by which inequality has its effect on behaviour remain to be elucidated. It may be that local-level inequality is most salient psychologically (Wilson & Daly, 1997), which would render country-level inequality a proxy measure. The theory that cognitive processing limits people to maintaining relationships with around 150 people – Dunbar’s number (Dunbar, 1993) – would suggest that the relevant traits of this group are particularly important to an individual’s perception of LH traits in the social environment. The influence of aspects of the social environment isn’t necessarily conscious however (Wilson & Daly, 1997).

In experimental psychology, priming participants with varying levels of inequality would be expected to elicit varying responses if they were then tested on LH relevant measures. Systematic differences in attraction and personality could be further investigated. In a game theoretical approach, inequality could be introduced into public goods games like the iterated prisoner’s dilemma. A tournament like that run by Axelrod (2006) would be predicted to turn out different strategies as winners under varying conditions of inequality. Cooperation would be expected to be more widespread when inequality is lower, and defection more common when inequality is higher.

If the theory that income inequality pushes LH strategies toward the faster end of the spectrum is supported, this would provide a policy lever for changing LH strategies. The facilitation of the slow LH strategy may be warranted in safe environments with plentiful resources (Richardson & Hardy, 2012). In general, the failure of education campaigns in effecting behaviour change would be more understandable, and policies that alter the social environment would be encouraged.

 

 

References

Anderson, L.R., Mellor, J.M. Milyo, J. 2004 Social capital and contributions in a public-goods experiment. American Economic Review 373-376.

Axelrod, R. 2006 The evolution of cooperation: revised edition. Basic books.

Brooks R., Scott I. M., Maklakov A. A., Kasumovic M. M., Clark A. P., Penton-Voak I. S. 2011 National income inequality predicts women’s preferences for masculinised faces better than health does. Proc. R. Soc. B 278, 810–812.

Brumbach, B. H., Figueredo, A. J., & Ellis, B. J. 2009 Effects of harsh and unpredictable environments in adolescence on the development of life history strategies: A longitudinal test of an evolutionary model. Human Nature 20, 25–51.

Daly M., Wilson M., Vasdev S. 2001 Income inequality and homicide rates in Canada and the United States. Canadian Journal of Criminology. 43, 219–236.

DeBruine L. M., Jones B. C., Crawford J. R., Welling L. L. M., Little A. C. 2010 The health of a nation predicts their mate preferences: cross-cultural variation in women’s preferences for masculinised male faces. Proc. R. Soc. B 277, 2405–2410.

Dickins, T.E. 2012 Teenage Pregnancy in the United Kingdom: A Behavioural Ecological Perspective. Journal of Social, Evolutionary, and Cultural Psychology 6, 344-359.

Dunbar R.I.M. 1993 Coevolution of neocortical size, group size and language in humans. Behav. Brain. Sci. 11, 681–735.

Ellis B.J., Figueredo A.J., Schlomer G.L. 2009 Fundamental dimensions of environmental risk: the impact of harsh versus unpredictable environments on the evolution and development of life history strategies. Hum. Nat. 20, 204-268.

Figueredo, A. J., Vásquez, G., Brumbach, B. H., Schneider, S., Sefcek, J. A., Tal, I. R., et al. 2006 Consilience and life history theory: From genes to brain to reproductive strategy. Developmental Review, 26, 243–275.

Kruger, D. J. 2010 Socio-demographic factors intensifying male mating competition exacerbate male mortality rates. Evolutionary Psychology 8, 194–204.

McMillen IC, Robinson JS. 2005. Developmental origins of the metabolic syndrome: Prediction, plasticity, and programming. Physiol .Rev. 85, 571–633.

Nettle, D. 2010a Dying young and living fast: Variation in life history across English neighbourhoods. Behavioral Ecology 21, 387-395.

Nettle, D. 2010b Why are there social gradients in preventative health behavior? A perspective from behavioral ecology. PloS one 5, e13371.

Neville, L. 2012 Do economic equality and generalized trust inhibit academic dishonesty? Evidence from state-level search-engine queries. Psychological Science 23, 339-345.

Pickett K.E., Mookherjee J., Wilkinson R.G. 2005 Adolescent birth rates, total homicides, and income inequality in rich countries. Am. J. Public Health 95, 1181–83.

Richardson, G. B., Hardesty, P. 2012 Immediate survival focus: Synthesizing life history theory and dual process models to explain substance use. Evolutionary Psychology, 10, 731-749.

de Vries, R., Gosling, S., & Potter, J. 2011 Income inequality and personality: Are less equal U.S. states less agreeable? Social Science & Medicine, 72, 1978-1985.

Wilkinson R. G., Pickett K. E. 2009 The spirit level: why more equal societies almost always do better. London, UK: Penguin.

Wilson, M. & Daly, M. 1997 Life expectancy, economic inequality, homicide, and reproductive timing in Chicago neighbourhoods. Br. Med. J. 314, 1271–1274.

How Labour can Explain Inequality

Ed Miliband has already said he will put the idea behind The Spirit Level at the heart of his manifesto. He recognises that the body of evidence cited in the book has massive implications for Labour’s policies. The history of scientific ideas entering mainstream politics is not auspicious though. Climate change and drugs are two examples of issues where policy lags disastrously far behind scientific evidence.

Logo Labour Party UK

Some people hold entrenched views on either side of any debate, but answering why some open-minded people aren’t convinced by the evidence is key to shifting the weight of public opinion. The answer lies in those people failing to engage with the evidence – it takes a certain way of thinking to absorb data and construct a coherent explanation of it. Too often evidence is presented in isolation, in a didactic manner, and with no reference to the underlying causes. Labour needs to explain not merely that inequality is harmful, but why inequality is harmful.

If the numerous correlations of inequality and bad outcomes in The Spirit Level are simply held up as irrefutable evidence, they will be refuted by ideological opponents (as they already have been) and claimed to be politics-based evidence. Labour needs to dig beyond the correlations to the underlying causation, because the general public are much more likely to latch on to a narrative of how inequality changes behaviour. This will be more comprehensible, logical, memorable, and much easier to rally round as a cause than dry statistics.

This format is too short to fully explain why inequality is harmful, but a brief account follows. Humans are a highly socially hierarchical species. Game theoretical models show that cooperation between people is adaptive when the hierarchy is relatively equal. This is because there isn’t much to gain by trying to get ahead of someone else. The more unequal it becomes however, the more one stands to gain by moving up the hierarchy – or lose by going in the opposite direction. So cooperation is less adaptive, and people behave more competitively in an attempt to get one over on others. Social status becomes the be-all and end-all.

This competitive behaviour and the anticipation of being on the receiving end of it leads to a decrease in trust. People also become more stressed and anxious as a result. Unhealthy (comfort) eating increases which in turn increases obesity. Drug abuse goes up as people self-medicate. The extreme social pressure leads to much more mental illness. Children forced to grow up too fast are less well educated and have more teenage pregnancies. People obsessed with their social status react more violently to being disrespected. And needless to say, social mobility languishes.

Inequality changes the rules of the game, and brings out the worst in our malleable human nature. Labour could highlight this fact to those who have a pessimistic view of human nature. And they could finally offer an alternative model of society to the current broken system, one grounded in science not ideology.

The Evolutionary Psychology of Inequality

This index measures the degree of inequality i...

Income inequality by country

Income inequality is used as the principle measure of economic inequality by the authors of The Spirit Level, though they acknowledge that it is an incomplete measure. It fails to account for savings or property, but is employed as a reasonably simple and widely available statistic. Social capital may be the real driving force behind outcomes, contend the authors, but it may not correlate perfectly with wealth – a poor person with a wide social network may fare better than a rich loner.

So income inequality may be acting as a proxy not only for overall wealth but social capital too. From an evolutionary perspective, it is unlikely that wealth alone is the best predictor of outcomes.

The social hierarchy provides a more complete explanation for why less unequal societies do better. In every society, natural and sexual selection operate on individuals relative to other people in the same society. It is because of this that relative poverty rather than absolute poverty is the determining factor in outcomes in rich countries.

Concepts of behaviour being ‘for the good of the species’ always missed the point because competition is fiercest between individuals of the same species. This is because the resources they compete for – food, habitat, mates – are exactly the same ones their conspecifics want.

In hierarchical primate species, those further up have better access to resources. Presumably the bigger the social gap, the bigger the gap in access to resources. In humans, the manifestation of the gap in access to resources is financial wealth. It seems unlikely that Americans are much more spread out in terms of innate ability than Danes or Norwegians, so it isn’t the case that the income structure of a country reflects natural justice. Rather, income structure determines people’s access to resources.

But because we intuitively associate people’s wealth with their place in the social hierarchy, the poor are more likely to be seen as deserving to be poor in more unequal countries. Because of this, less help is given and there is less political will to reduce inequality. This forms a vicious circle and a self-fulfilling prophecy between the justification of extreme inequality and its presence.

In reality I think it is likely that position in the social hierarchy correlates very strongly with income, but is a better predictor of outcomes. Even it would still fall short of predicting outcomes perfectly though. An assumption of this is that the social hierarchy isn’t simply ordinal; it can have differently sized gaps between people – some alpha males are more alpha than others.

Our societies will always be hierarchical – as attempts at complete egalitarianism in the past have shown, some will always be more equal than others. But between this extreme and the current levels of inequality in modern societies, there must be a sweet spot – an ideal level of inequality. This would not be determined by ideological imperative, but would be measurable on the health and social outcomes used in The Spirit Level.

Apart from the revolutionary effect that the knowledge of the importance of inequality will have on government policy, it represents a chance for evolutionary psychology to shake off the chequered history of its previous incarnations. Applying Darwinism to societies in the past led to inhumane ideologies like Social Darwinism and eugenics. Now, it has the chance to explain why, far from championing  survival of the fittest, cooperation should be favoured over competition, for the benefit of everyone.

Rising above our nature

Kipling's exceedingly good prediction

Evolutionary psychology is based on the idea that complex human behaviour can be explained by virtue of its adaptiveness. If a trait is maladaptive today, it will have been adaptive when the trait evolved, for example a sweet tooth leading to obesity these days would have been useful in the savannah where high-energy foods were scarce. This type of reasoning has attracted criticism of being just-so stories, due to the lack of available evidence, even if the logic seems plausible.

But what if we stuck to traits that have such a direct effect on survival and reproductive success that their adaptiveness couldn’t be disputed? Survival and reproductive success are the two strongest instincts, because these are the only two criteria natural selection acts on. Every other trait that is selected for is only chosen because of its effect on these two criteria. A trait can even benefit one at the expense of the other, which lead Darwin to differentiate between natural and sexual selection (e.g. the peacock’s tail – a ‘handicap’ display to advertise to the peahen its fitness, that it can survive despite having to grow it and carry it around).

These two strongest instincts we share with every other life form on earth, it’s just we’re (probably) the only ones who know it. You are the direct descendent of billions and billions of individuals, all of whom were better at surviving and reproducing than at least some others in their generation. Put like that, the evolution of complex life sounds at least intuitively more plausible.

So that’s two things we’re pretty good at, but is there anything else we’d like to do with ourselves now that we’ve evolved consciousness? The pursuit of happiness is one such goal, but research shows that, unsurprisingly, we need to pander to our instincts to be content. Comparing the income of a country with its happiness shows that initial gains in income lead to huge gains in happiness, but with diminishing returns after a basic subsistence level is reached. A similar pattern emerges if income is compared with life expectancy, so life expectancy would be a very good predictor of happiness – no surprise given the strength of the survival instinct.

Unfortunately as far as people in rich countries are concerned, economic wealth only improves wellbeing up to a point – which may represent a ceiling in human happiness. According to the authors of The Spirit Level, this is where absolute poverty stops being the limiting factor, and is replaced by relative poverty (economic inequality within a society). The evidence for a correlation between inequality and unhappiness is mixed, but the Nordic countries are among the happiest.

The evidence is much stronger for inequality diminishing societal wellbeing, and reducing mental illness, infant mortality etc. are laudable goals in themselves. The worse behavioural outcomes in more unequal countries are an evolutionary hangover, which can inform efforts to improve societies. People behave in ways that improve their place in the pecking order. All social primates are hierarchical to a greater or lesser extent, and position in the hierarchy is a strong predictor of survival and reproductive success. It is no longer as important for humans in rich countries, as resources are plentiful, so everyone can live and have children. In harsher environments like our evolutionary past, those lower in the hierarchy faced an earlier death and less chance of reproducing, so we have evolved a very strong instinct to climb the social ladder.

This instinct is mediated by the environment, however: it is less appropriate in an egalitarian context, where resources are shared out fairly. But it comes into its own in an unequal society, where being at the bottom of the pile could mean genetic oblivion. By this mechanism inequality leads to lower levels of trust, dealt with in an earlier post, and numerous other negative outcomes, which I’ll cover in future.

Inequality and Game Theory

A spirit level

Image via Wikipedia

The link between income inequality and negative health and social outcomes is supported by a large and growing body of research. More economically stratified countries have higher infant mortality rates, levels of mental illness, obesity, lower levels of social mobility and trust, and numerous other worse outcomes. The evidence is reviewed in a recent book called The Spirit Level, and summarised by the authors on The Equality Trust website. A key part of their explanation of the evidence is the idea that people can behave either cooperatively or competitively towards each other, and do so in varying ratios depending on the level of inequality.

The concept of the selfish gene meaning that individuals will always behave selfishly is a fallacy that has long been debunked. Cooperation between members of a species is known as reciprocal altruism, which used to be held up as evidence for group selection: individuals doing things for the good of the species. But this model is susceptible to freeloaders, who benefit at the expense of the other group members; a model was needed that allowed for cooperation as well as punishment of selfish individuals.

In 1984, Robert Axelrod held a computer-simulated tournament to find the most successful strategy in a population of individuals who could cooperate with each other, or defect. It was based on repeated rounds of the prisoner’s dilemma, a problem from game theory. In each round, points were allocated to each player dependent on their actions (see payoff matrix). The winner was a program called Tit-for-Tat, which cooperated with its opponent on the first go, and copied its opponent’s previous move thereafter. This allowed for mutually beneficial cooperation cycles to occur, but if its opponent defected continually, Tit-for-Tat prevented exploitation by defecting too.

  Player 2
Cooperate Defect
Player 1 Cooperate Both: 3 Player 1: 0Player 2: 5
Defect Player 1: 5Player 2: 0 Both: 1

 

What the tournament showed theoretically was that reciprocal altruism evolves when it benefits individuals (any group benefit is a consequence). Being vigilant to selfish individuals is essential though, to prevent being taken advantage of. In modern societies, everyday life is full of chances to cooperate or compete with others. The ratio of cooperation to competition within a society is reflected in its emphasis on collectivism or individualism. Decisions don’t take the exact form of the prisoner’s dilemma, but it provides a useful way of thinking about behavioural differences. However, it only predicts how a given individual will behave in a given population, not how different populations will vary from each other.

So how can game theory be applied to the differences between societies identified in The Spirit Level? Trust would seem to be a critical factor in people’s choices in the prisoner’s dilemma, and trust is in shorter supply in more unequal countries. This may be a rational response to the effect inequality has on the relative payoffs of cooperation and competition. When the rungs of the social ladder are further apart, there is more to be gained or lost in competition with others. In the prisoner’s dilemma, the points can be considered to represent gains or losses to be made, relative to others, in the hierarchy of social status. Inequality increases the viability of selfishness firstly because there is more to be gained by acting selfishly when the other cooperates, and secondly there is more to be lost by cooperating when the other acts selfishly (see new payoff matrix).

  Player 2
Cooperate Defect
Player 1 Cooperate Both: 3 Player 1: -5Player 2: 10
Defect Player 1: 10Player 2: -5 Both: 1

 

The theory is testable, and predicts that people in more unequal countries are more likely to defect in the prisoner’s dilemma than people in less unequal countries. Cross-cultural studies have mostly compared individualistic and collectivist cultures, and attribute the higher level of cooperative behaviour in collectivist cultures to differing social norms. But this explanation doesn’t explain what causes the differing social norms. Differing levels of inequality could predict levels of collectivism, social norms and levels of cooperation.

The prisoner’s dilemma is just one of many games based on a trade-off between individual gain and the common good. The uplifting message from both the game theory tournament and the research behind The Spirit Level is that the two are not mutually exclusive.